The present invention relates to trailers that are towed by another vehicle using a fifth-wheel hitch or a gooseneck hitch. Generally, the pin box of the fifth-wheel hitch extends from the bottom of the foremost section of the trailer and attaches to a female receptacle connected to the bed of the towing vehicle, typically over the rear axle of the towing vehicle. A substantial number of the forward sections of nearly all fifth-wheel trailers must extend over the bed of the towing vehicle in order to utilize a fifth-wheel hitching system. Therefore, the lower parts of the forward sections of fifth-wheel trailers, including the floor, are typically required to be significantly higher than the floors of the remaining, main sections of trailers in order to provide sufficient clearance to extend over the back of the towing vehicle. In common designs of such trailers, the usefulness of this forward section is reduced because it is often not a full-height living space and does not permit users of average height to stand upright comfortably in the space. Additionally, steps must be placed between the main section of the trailer and the raised front section. These steps make use of this area awkward and potentially hazardous.
In an attempt to maximize the usefulness of this space, most current models of fifth-wheel trailers use this forward section of the trailer as a bedroom. In some designs, the roof is made taller over this forward section to make it more comfortable and spacious. These solutions may provide a slightly more comfortable interior space, but they are not optimal by any any means. First, the bedroom must be located in this forward section of the vehicle reducing the number of potential floor plan options. Second, this forward section is often not the full height of the trailer, which makes standing in this area impossible or very uncomfortable for a person of average height. Activities that are usually performed in this section can be difficult without the benefit of a full-height space. Third, the floor of the bedroom area is not the same height as the floor of the rest of the trailer, requiring the use of steps to gain entrance to this forward section. Steps are not easily navigated by all people and care is required to deal with the tripping and falling hazard posed by an uneven floor. Finally, some current models elevate the ceiling of the forward section of the trailer to provide greater height to the inside living space. However, by extending the roof of the vehicle upward, the trailer becomes less aerodynamic and more strain is placed on the hitch and towing vehicle, resulting in instability, reduced gas mileage and reduced life of the vehicles and hitching mechanism. Additionally, raising the roof does nothing to alleviate the height difference between the floor of the forward section of the trailer and the floor of the main section of the trailer. In other words, steps are still required even after the roof has been raised.
Several attempts have been made to provide a fifth-wheel trailer that has a full-height forward section. However, these have not been safe or practical and have not been accepted by the market. The pin box for hitching the trailer to the towing vehicle has been attached to a movable structure, such as a wall panel that is hinged into place and acts as one of the walls for the lower section when the floor is lowered. See U.S. Pat. No. 4,085,959. This placement of the metal pin box on a movable piece is not desirable because the structure supporting it is not substantial enough to allow for safe hauling. A wall panel cannot provide the necessary structure to resist the forces exerted on the trailer while it is being moved and will damage or destroy the panel. Additionally, the pin box must be made of metal or other heavy material. Placing a large heavy object on a part of the trailer that can easily become loose and rotate about a hinge is dangerous and could cause extensive damage to the vehicle and possibly cause serious injury to operators or bystanders. These problems would only be further exacerbated by today's larger and heavier trailers.
What is needed is a trailer having an adjustable-height floor in its forward section that is capable of being towed using a fifth-wheel hitch and can provide a full-height living space when not hitched to a towing vehicle. The main support frame of the trailer must have a shape, which can allow up and down movement of the floor of the front section of the trailer, but also be capable of supporting the weight of the trailer. The front section's adjustable floor should also be safe and easy to operate.